1. Field of the Invention
The present invention relates to a nacelle apparatus for an airplane of the type having nacelles for jet engines mounted under a wing, particularly to a nacelle apparatus which has improved lift/drag properties brought about by reducing a magnitude of drag due to aerodynamic interference of the wing with each nacelle during flying of the airplane at high speed.
2. Description of the Related Art
To facilitate understanding the present invention, a typical conventional nacelle apparatus for an airplane of the foregoing type will be described below with reference to FIG. 6.
As shown in the drawing, the airplane of the type having jet engines mounted under a wing 1 includes nacelles 3 which are suspended from the wing 1 via pylons 2. However, it has been already known that a lift/drag ratio of each jet engine is reduced under the influence induced by aerodynamic interference of the wing 1 with the nacelles 3 when each nacelle 3 is located excessively near to the main wing 1.
On the other hand, in the case of this type airplane having jet engines each having a large bypass ratio mounted from the wing, it is required that landing gears and pylons are elongated. In this case, since the weight of the airplane is unavoidably increased, it is necessary that the elongation of the landing gears and the pylons is suppressed. On the contrary, however, when the length of each pylon is shortened, a magnitude of interference drag induced by aerodynamic between the wing and the nacelle is correspondingly increased. In addition, shortening of the length of each landing gear is limitatively restricted from the viewpoint of safety because of a necessity for maintaining a necessary clearance between the lower surface of each nacelle and the ground surface. In connection with the conventional nacelle apparatus constructed in the above-described manner, a technical measure for suspending the nacelle under the wing with a sufficiently long distance kept therebetween has been generally taken because no occurrence of aerodynamic interference of the wing with the nacelle is significantly taken into account. In addition, another technical measure for reducing a magnitude of aerodynamic resistance induced by the interference of the wing with each nacelle by correctively modifying the contour of each nacelle cowl has been developed for practical use in association with a nacelle apparatus as disclosed in an official gazette of U.S. Pat. No. 4,799,633.
However, since the aforementioned technical measure for mounting the nacelles under the wing with a sufficiently long distance kept therebetween induces substantial increase of the weight of the airplane due to elongation of the landing gears and pylons, it is not preferable to practically employ the aforementioned technical measure.
With the last-mentioned technical measure for correctively modifying the contour of the nacelle cowl, there arises a necessity for changing the contour of the whole nacelle from a simple cylindrical contour to a complicated one. Due to the foregoing necessity, it is difficult to fabricate the optimum nacelle apparatus, resulting in a fabrication cost of the nacelle apparatus being undesirably increased.